Over the past year, we have collected 102 pedigrees of centenarian probands. This data, when compared with the pedigrees of a similar birth cohort (born in 1896) which died at the age of 73 years (n=77) has yielded two important findings indicating aggregation of longevity within families: 1. The siblings of the septuagenarian probands had 2.3 times the rate of death at any given age beyond age 65. The relative risk of survival steadily increased with age for siblings of centenarians to the point that they had 2.9 times the risk (95 percentCI: 1.01, 8.42) of surviving to age 91 years. Relative risks were greater for men than for women. Because the two comparison groups were similar birth cohorts, our findings support the increasing importance with age of inherited factors which promote longevity. 2. In the process of recruiting subjects we found two families impressive for the penetrance of extreme longevity within a single generation. One family had 4 centenarians and 1 nonagenarian and another had 3 centenarians and 1 nonagenarian. The ages of these siblings have been confirmed by multiple forms of proof including birth certificates and entries in the 1900, 1910 and 1920 federal censuses (2). The two immediate goals of the study are therefore: 1. To increase the sample size of both the centenarian and septuagenarian birth cohorts. Data collection from more families will allow us to determine survival risk ratios for even older ages and confirm (or disprove) that the risk ratios become larger and larger with extreme age. 2. To continue our search for families with multiple centenarian siblings and to verify their ages using family reconstitution methods and other resources such as the U.S. census archives. We hypothesis that families such as these are more common than previously believed because of the strong genetic influences that must be present. Collecting a series of such families would be the first step in characterizing both pedigree patterns, and then later, genetic loci that they may have in common.